Epidermis - Bernstein Medical - Center for Hair Restoration
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Dr. Bernstein summarizes an article on stem cells that was published in the journal Nature:

This study demonstrates that after wounding the skin of an adult mouse, an embryonic-like change in the epidermal cells outside of the hair follicle stem cells can be induced to form new hair follicle stem cells. In other words, these cells originate from epidermal skin cells in the wound, but then are able take on the characteristics of hair follicle stem cells and actually produce hair. These regenerated hair follicles establish a stem cell population that can produce a hair shaft and continue through all stages of the follicular cycle. The research suggests that these regenerated hair follicles grow new hair through the introduction of Wnt proteins.

The technology, developed at the University of Pennsylvania School of Medicine, has been licensed by Follica Inc. a privately held medical device company.

Reference: “Hair Follicle Regeneration in Adult Mouse Skin After Wounding,” Ito, M., et al. Nature 447, 316-320, May 17, 2007

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Q: I am considering having an FUE procedure and have heard the phrases topping, capping, and tethering as part of the procedure. What do all these terms mean? — C.C., Hell’s Kitchen, N.Y.

A: These are all terms that refer to the types of injury that can occur to grafts during a follicular unit extraction procedure.

In FUE, a sharp instrument (or sharp instrument followed by a blunt one) is used to separate follicular units from the surrounding donor tissue. Forceps are then used to remove the follicular units from the scalp.

Topping occurs in the first step when the doctor accidentally cuts off the top of the graft so that the remainder of the graft cannot be removed.

Capping occurs when the doctor grabs a graft with forceps and the top of the graft (the epidermis and upper dermis) pulls off, leaving the rest of the graft behind.

Tethering occurs when the bottom of the graft is still attached to the deeper tissues after the first step causing the follicular unit to pull apart during extraction.

There are a few other terms used as well.

Shredding occurs when the follicular unit is not totally separated from the surrounding tissue and pulls apart upon extraction. Shredding can also occur when the follicular unit was partially damaged in the first step.

Transection is like topping, but here the mid or lower portion of the hairs in the unit are cut.

Buried grafts occur when the graft is pushed into the sub-cutaneous space rather than extracted. Buried grafts can usually be removed, but if not removed completely, may turn form small cysts.

Visit the Follicular Unit Extraction page.

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Q: What can be done if I want to have a hair transplant and my scalp is very tight from prior surgeries? — R.R., Long Island, N.Y.

A: Follicular Unit Extraction is ideal in very tight scalps, provided that there is enough hair to extract without leaving the donor area too thin and provided that the follicles are not too distorted from the scarring.

With strip harvesting, undermining techniques may be helpful to close the wound edges once the strip is removed.

In undermining, the surgeon uses either a sharp instrument (scalpel) or blunt instrument (the dull edge of scissors) to separate the upper layers of the scalp (dermis and epidermis) from the lower part of the scalp (fascia). The hair transplant surgeon accomplishes this by spreading apart the fat layer of the skin or by cutting through scar tissue.

Undermining allows the upper layers of skin to literally slide over the lower layers and can significantly increase the ability to close a tight wound. However, if not done carefully, it may increase the risk of bleeding and injury to nerves and occasionally may damage hair follicles.

Undermining is usually used with a layered closure where the deeper tissues are brought together first with a layer of absorbable sutures before the surface of the skin is sutured closed with sutures that are removed.

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